Why does my website have an old copy cache date?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Mauro MADONNA: Do you Know why my website have the date of copy cache on 21/October ?
  We are at 27 November!In Webmaster Tool i have given sitemap,robot is ok, htacces is ok, View as Google is ok.
  Do you Know why?  ;
• 
  Federico Sasso: To strictly answer your question, my best guess is this is due to the fact your web server returns this HTTP header: " Expires: Thu, 19 Nov 1981 08:52:00 GMT "
  Aside note: given the fact your web site today has no content (beside the boiler plate), I'd be rather glad Google keeps the old cached copy.
• 
  Dave Elliott: i read an article that this is happening for a lot of sites at the moment.
  
  https://www.seroundtable.com/google-cache-dated-19497.html
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  Piyush Vasoya: +Mauro MADONNA ; Same issue here in my 10+ sites after penguin 3.0 ;
• 
  Shirley Dixon: mines states Not Found!!!
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  Mauro MADONNA: +Shirley Dixon ; why not found? It is visible, perfect!
  +Dave Elliott ;i have read but isn't a solution :(
  +Piyush Vasoya ; have you found the problem?
• 
  Federico Sasso: I gave a 2nd read to my answer, and realized the expire is 1981, I don't know why I perceived it as 2081 :)
  Have a look at your site, though, you have empty content, probably because a db connection failure.
• 
  Shirley Dixon: Sorry i may have mislead you. I meant when checking the last crawl by googlebot.
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  Mauro MADONNA: +Shirley Dixon ; googlebot also 24 November crawl on my site
• 
  Dave Elliott: cache date seems to have been updated now. ;https://www.seroundtable.com/google-cache-updated-19509.html
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  Mauro MADONNA: Yes i confirm have benn updated